JP2007288190A - Structure for generating extreme ultraviolet light from a plasma with high conversion efficiency and minimal contamination generated by an energy beam - Google Patents

Abstract

An energy beam induced plasma that allows efficient conversion of an energy beam (4) into EUV light in a wavelength region near 13.5 nm and ensures a long life of an optical system component and an injection unit (13). Find new possibilities for EUV light generation by (5).
When a mixture of particles (14) and a carrier gas (15) is used, the target supply device (1) has one gas liquefaction chamber (12), in which the target material is liquefied carrier. Drops to be supplied to the jet unit (13) as a mixture (16) of solid metal particles (14) in a gas (17) and to produce a predetermined drop size and drop row (2) A generator (131) is provided, in which the ejection unit (13) is triggered by the pulse frequency of the energy beam (4) to generate a droplet train (23), depending on the frequency. Controllable means (132; 135, 136, 137, 138; 31, 32) are connected.
[Selection] Figure 1

Description

  The present invention is directed to generating an extreme ultraviolet (EUV) light from a plasma with high conversion efficiency generated by an energy beam and directed to an interaction position with the target in the plasma generation chamber. A supply device forms a mixture of particles of target material with high luminous efficiency and at least one carrier gas, and an amount capable of converting the target material with high luminous efficiency into radiation by an energy pulse. The present invention relates to a structure having an injection unit for metering and discharging a predetermined target volume into a plasma generation chamber in order to enable supply. The present invention is particularly applicable to a light source for EUV lithography for manufacturing semiconductor chips.

  Known "clean fuels" (for example target materials such as xenon) have a conversion efficiency (ratio of energy emitted in the desired EUV spectral band to (laser) excitation energy) of only about 1%. Furthermore, it is not efficient enough to generate EUV light based on plasma excited by an energy pulse beam and emitted in the EUV spectral band near 13.5 nm. This clean fuel means that there is no “cloudiness” generated on the surface (particularly in the optical system) due to the components of the light source, that is, there is no precipitate (contamination) generated on the surface. Yes. In order to generate EUV near 13.5 nm, metal target materials (for example, elements from Group IV to Group VII in the fifth period of the Periodic Table of Elements) are much more efficient (for example, Although the conversion coefficient of tin is about 3%), it is "cloudy", i.e. it generates debris upon plasma excitation, which causes, among other things, precipitation on the surface of the light source, especially on the optical components. In addition to coming, the application will come. In addition, the application process (corrosion of the optical system surface) caused by the high kinetic energy of the unburned target particles that are not converted into luminescent plasma is a “clean fuel” (eg xenon) compared to metal target materials. ) Is much less.

  Pure tin (Sn) provides a broad spectrum around 13.5 nm ± 2% (the desired spectral band for semiconductor lithography, so-called “in-band EUV light”), but the desired EUV for semiconductor lithography. The ratio of the out-of-spectrum band (so-called “out-of-band EUV light”) is also significant. This “out-of-band” light portion is undesirable because it contributes unnecessarily to heating the source optics and other components.

  In order to use a metal-containing target, it is known in the prior art that a metal solution is used at room temperature as a spot target for spot plasma generated by a laser. In this regard, Patent Document 1 describes, as metal solutions, metal chloride, bromide, sulfide, and nitride solutions, and organometallic solutions, particularly copper compounds and zinc compounds. Since almost no debris is generated, the present invention can be applied without causing damage around the optical system component. The radiation produced, however, is substantially limited to the 11.7 nm to 13 nm range, which is classified as part of the “out-of-band” light in the spirit of the above requirements of EUV lithography. In Patent Document 2, the same situation is explained by adding a tin compound, particularly tin chloride.

  As disclosed in U.S. Patent No. 6,047,033, it is possible to limit the amount of target material that can be converted by injecting the droplets as a liquid (e.g., tin compound or nanoparticles). However, all known carrier liquids or solvents for this purpose are disadvantageous in that they contain components (carbon: cloudy, oxygen: oxidation) that damage the optical system.

Patent Document 4 describes an X-ray and EUV light generator, in which the atomic density is> 10 for the purpose of increasing the target density of the minimum (on the order of the laser wavelength) droplets. It is assumed that a mist of ⁸ atoms / cm ³ is generated. The target density is improved by connecting a valve that can be switched to an electromagnetic type to an ultrasonic nozzle via an expansion passage provided with a heating means for raising the temperature. Is supplied to the plasma generation process in a pulsating manner by bringing the liquid target into a non-reactive gas. The disadvantage here is that the dispensing procedure is complicated and that the target density rapidly decreases after exiting the target nozzle.

  In the gas phase injection of nanoparticles in a carrier gas as described in Patent Documents 5 and 6, the “gas cloud” containing the particles expands fairly rapidly, and as a result, a little distance (about 1 cm) from the injection point. As a result, for example, the density becomes too small for efficient excitation by a laser, for example, so that the concentrated state is generally insufficient. For this reason, excitation must be performed in the vicinity of the injection port, and the restriction of the amount of particles to a quantity that is essential for complete conversion of energy cannot be easily realized.

  The possibility of the distribution of the solid target material is disclosed in Patent Document 7 anyway. There is a chamber system in which the solid or liquid target clusters are mixed in the gas in the first chamber. From there a “focused mass flow” is generated in the second chamber, which passes through a periodically opening closure device and reaches the third chamber where the plasma is generated as a pulsating mass flow, whereby the laser pulse Each time a necessary amount of convertible target material is prepared, thereby reducing the proportion of unconverted target material in the plasma chamber. The target material blocked by the closure device in the second chamber is aspirated and thereby made available for reuse.

US Pat. No. 6,831,963 US Patent Application Publication No. 2004/0208286 International Patent Application Publication No. 2002/46839 International Patent Application Publication No. 2004/056158 European Patent No. 0858249 US Patent Application Publication No. 2004/84592 International Patent Application Publication No. 2004/088452

  The problem to be solved by the present invention is that when a metal target material is used, EUV light in the wavelength region near 13.5 nm without damaging subsequent optical components due to debris generated due to the surplus target material. It is to find new possibilities for the generation of EUV light by an energy beam induced plasma that allows an efficient conversion of the energy beam into. Furthermore, in order to guarantee the long life of the injection device, generation of radiation at a large distance from the injection device is realized by the supply method of the target material.

A further extension of the present invention is
(A) Suitable for efficient absorption of laser light of about 1 μm,
(B) contributing to narrowing the emission band of the spectrum to 13.5 nm,
(C) In addition to the stake in the metal target, it does not contain any components that damage source components important for function,
The object is to find a jetting method of a metal target material.

  This object is achieved by the present invention in which a pulsed beam of energy is directed to an interaction position with a target in a plasma generation chamber for generating extreme ultraviolet rays from a plasma having a high conversion efficiency generated by the energy beam, and supplying the target. The device supplies a mixing chamber for forming a mixture of particles of target material with good luminous efficiency and at least one carrier gas, as well as an amount of target material with high luminous efficiency that can be converted into radiation by an energy pulse. In order to be able to do so, the target supply device has one gas liquefaction chamber in a structure having an injection unit for metering and discharging a predetermined target volume into the plasma generation chamber. In that case, the target material is liquefied carrier gas. Droplet generation with a nozzle chamber and a target nozzle to be supplied to the injection unit as a mixture of solid metal particles therein and for the injection unit to generate a predetermined droplet size and row of droplets In order to produce a time-controlled row of droplets, the jetting unit is connected to the jetting unit by means of a frequency-dependent controllable trigger triggered by the pulse frequency of the energy beam. Is solved.

  The liquefaction chamber is advantageously placed after the mixing chamber so that the solid particles are mixed with the carrier gas and sent to the liquefaction chamber, the liquefaction chamber being configured to liquefy this particle-gas mixture. .

  In another preferred variant, the liquefaction chamber is placed in front of the mixing chamber, so that the liquefaction chamber is configured to liquefy clean carrier gas and the mixing chamber is configured to mix solid particles with this liquefied carrier gas. Is done.

  The solid particles having good luminous efficiency are advantageously composed of tin, a tin compound, lithium or a lithium compound. In this case, the solid particles preferably have a size of less than 10 μm, preferably in the nanometer range, and are therefore referred to below as nanoparticles (without constraining generality).

  As the carrier gas, it is advantageous to use an inert gas such as nitrogen or a rare gas. Very suitable is argon. In order to limit the emission spectrum bandwidth of EUV to around 13.5 nm, that is, to suppress out-of-band light, in addition to such a carrier gas selected as the main component, a light noble gas (eg, helium, neon) ) Is preferably added.

The diameter of the individual targets (droplets) ejected from the ejection unit is advantageously between 0.01 mm and 0.5 mm.
In order to reduce contamination by surplus target material, it is very useful if the target nozzle of the injection unit is followed by means for removing the individual target, so that the vibration of the individual target reaching the interaction position It has been found that several periods exactly match the pulse frequency of the energy beam.

  In a first variant that is advantageous for this purpose, an electric or magnetic deflection is used to selectively deflect unwanted individual targets to the target nozzle of the ejection unit from the droplet stream emitted from the target nozzle. Means are postponed.

  In the second embodiment for removing the individual target, the individual target is shielded or passed in a predetermined form from the droplet row supplied from the target nozzle downstream of the target nozzle of the ejection unit. These mechanical closing means (for example, mechanical flaps, chopper wheels) are provided.

  The third modified example is arranged adjacent to the nozzle chamber so that the pressure in the nozzle chamber can be increased for a short time as needed in order to eject droplets one by one inside the ejection unit. A target generator with a pressure modulator and a nozzle in front of the target nozzle adapted to maintain a pressure adapted to the gas pressure of the gas supply in the mixing chamber higher than the plasma generation chamber Has an anterior chamber. This adaptation of the pressure in the nozzle chamber surrounding the target nozzle prevents unwanted dripping of the target material from the target nozzle, unless a pressure modulator generates pulse pressure. In order to appropriately adjust the pressure in the nozzle front chamber, the gas supply pressure in the mixing chamber is preferably adjusted to be slightly higher (high pressure of about 0.5 to 1 bar) than that in the nozzle front chamber.

  To prepare a liquid particle-gas mixture, a sufficient amount of particles are prepared in the reservoir and connected in series to the target generator so that it can be switched for continuous injection into the plasma generation chamber. It is also preferable that the particles are sent to a plurality of mixing chambers arranged in parallel.

  In a further advantageous variant, the particles are present in one mixing chamber in a mixed state with a carrier gas, and this mixing chamber has a conduit with another carrier gas supply pipe. A connection point is provided downstream, at which time at least one of the supply pipes routed to this connection point has a flow regulator, which calculates the amount of particles in the gas stream. The mixed carrier gas and the clean carrier gas are adjusted to a desired mixing ratio by being controlled by a measuring device placed behind the connection point. In this case, the measuring device for controlling the mixing ratio is preferably an optical unit for measuring scattered light.

The pulse beam of energy necessary for plasma excitation may be composed of at least one laser beam, electron beam, or ion beam.
The basic idea of the present invention is that when a metallic target material, especially tin, is excited using a pulsed beam of energy, the irradiated excitation energy is very high in the desired emission band around 13.5 nm. It is based on the consideration that it is efficiently converted (conversion efficiency is three times that of xenon that is conventionally used). For metals, however, it can only be introduced into a light source for EUV lithography if it can be guaranteed that it is sufficiently immune from contamination. This can be achieved by limiting the amount that is essential for the generation of radiation.

  The present invention addresses this problem by forming a mixture of solid metal particles (“nanoparticles” of particle size <10 μm) and an inert carrier gas, gas liquefaction, and dispensed droplets into a plasma generation chamber. It solves by combining with the injection of.

  A substantial increase in target density (relative to the buffer gas) by supplying a liquid mixture of solid metal particles and carrier gas into the plasma generation chamber using a jet device in the form of a droplet generator; And the distance of the target energy beam interaction position from the injection point can be greatly increased, so that radiation (conversion efficiency) on the one hand and contamination (injection nozzle damage due to debris) on the other hand are markedly increased. Will be reduced.

  By using a rare gas or nitrogen that does not contain any component that itself damages the optical system as a carrier medium, no new contamination is generated from the liquid target material produced as described above. . As the light emitter, Sn nanoparticles are preferably used. By adding a light carrier gas (helium and / or neon) to the main carrier gas, a spectrum band outside the EUV band which is undesirable for semiconductor lithography can be sufficiently increased. Suppressed in half.

A liquefied noble gas or liquefied nitrogen can also be used directly for the addition of particles.
The solution according to the invention makes it possible to generate EUV light by means of an energy beam induced plasma, which allows efficient conversion of the energy beam into EUV light in the wavelength region around 13.5 nm. Excess target material does not further damage subsequent optical components. In addition, since the distance of the plasma from the injection device can be increased, the life of the injection device and the stabilization of radiation generation can be ensured.

Next, the present invention will be described in detail based on examples.
The EUV light source has a target supply device 1, which in its basic structure—as schematically shown in FIG. 1—includes a mixing chamber 11, a liquefaction chamber 12, and a jet unit 13. It is out. Therein, the ejection unit 13 includes a droplet generator 131, a pressure modulator 132, a target nozzle 133, and a nozzle chamber 134.

In the mixing chamber 11, a metal or a metal compound having good luminous efficiency in the EUV spectral region (around 13.5 nm), for example, tin or lithium (or other oxides thereof, preferably SnO, SnO ₂ , LiO, LiO ₂ ). The solid particles 14 composed of the above and the like, and a clean (that is, no luminescent particles) carrier gas 15, such as a rare gas or nitrogen, are mixed together. The mixture 16 containing the particles resulting therefrom is sent to the liquefaction chamber 12, where liquefaction takes place at low temperature (T <173K) and pressure> 1 bar. In order to achieve high EUV generation efficiency (≈3%), it is preferable to add Sn particles (individual particle size is 10 μm at maximum). However, it is also possible to add other elements (eg lithium) or compounds (preferably tin compounds or lithium compounds).

  The addition of the particles 14 to the gas phase carrier gas 15 is configured so that the particles 14 and the carrier gas 15 are brought together in the mixing chamber 11—as schematically shown in FIG. From particle technology, several methods are known for breaking up prepared bulk particles and metering them into a gas particle. One possibility is to use a special rotating brush to remove the particles from the bulk particles one by one and deliver them to a carrier gas stream that strokes the brush. However, the particles 14 may be present in a sufficient amount in one mixing chamber 11, in which case switching between a plurality of mixing chambers 11 connected in parallel for continuous operation of the EUV source. Is done. The solid particles 14 can also be added to the liquefied gas 17 already present, as will be described in detail later with respect to the embodiment with reference to FIG.

  The liquefied gas 17 containing particles is supplied to the injection unit 13 and introduced into the nozzle chamber 134. With the help of a pressure modulator 132 (for example, a piezo actuator), a stable continuous droplet train 2 passes through the target nozzle 133 and corresponds to the frequency period of natural dripping of the liquefied gas 17 to the target shaft 21. Along the inside of the plasma generation chamber 3. The energy beam 4 is directed to a desired interaction position 41 on the target axis 21, and EUV is generated when the individual target 23 (droplet) passes through the interaction position 41 one by one by the continuous pulse. Excited by the light emitting plasma 5.

  The target supply device 1 is incorporated in the plasma generation chamber 3 by the case of the injection unit 13, and the case surrounding the target nozzle 133 of the injection unit 13 at that time constitutes the nozzle front chamber 135, An even higher pressure is set for the evacuated plasma generation chamber 3, thereby stabilizing the outflow of liquefied gas and the generation of droplets.

  The target supply device 1 is inserted into the plasma generation chamber 3 at some other position, for example, between the liquefaction chamber 12 and the jet unit 13 or at a supply pipe between the mixing chamber 11 and the liquefaction chamber 12. You may do it.

  In FIG. 1, a droplet jet 22 is first formed in a daisy chain (without constraining generality) and immediately after it exits the target nozzle 133, a stable series of individual targets (droplets) 23. By shifting to the row, the droplet row 2 of the individual target 23 is generated in association with the frequency period of natural dripping. In this case, each pulse beam 4 of energy usually does not hit all individual targets 23 (as schematically shown in FIG. 1). However, the droplet 23 in the recovery container connected to the vacuum pump (not shown) at the end of the target shaft 21 that has passed through the interaction position without being used is almost intact. Can be sucked out.

  The jetting of the liquefied gas 17 containing particles is performed so that droplets 23 of a desired size are formed. When the droplets 23 reach the interaction position 41, the plasma generation chamber 3 of the liquefied gas 17 is usually used. In this case, the spheres are solidified in order to be adiabatically expanded after being ejected into the vacuum, that is, after exiting from the (high-pressure) nozzle front chamber 135 and to freeze at that time.

  The size of the droplet 23 is defined by the amount of mixture that is optimally excited in the radiant plasma 5 by the predetermined energy of the pulse beam 4 of excitation energy. At that time, the amount of the solid particles 14 in the liquefied gas 17 is adjusted so that the EUV generation efficiency and the spectral width are optimized. Thereby, for the Sn particles 14 envisaged here, a quantity limitation is achieved, i.e. the amount of Sn in the plasma generation chamber 3 is limited to the quantity necessary for the generation of radiation, so that insufficient excitation As a result, no metal surplus target material remains in the plasma generation chamber 3 which could damage the light source components as debris.

If the carrier gas 15 (N ₂ or noble gas) can damage the optical system, it is at best due to the kinetic energy of the particles. Such a sputtering process can be easily suppressed, and for xenon-based EUV sources, for example, a gas that prevents sputtering between the plasma 5 and the collection optics (eg, a cross flow of argon). It is known to suppress by blowing. In any case, the carrier gas 15 itself does not contain any component that damages the optical system such as carbon (C) or oxygen (O ₂ ).

  By injecting a liquid mixture 16 containing particles, from all the critical components of the system, such as the target nozzle 133, a condensing optics (not shown) for focusing the generated EUV light, A very large distance of the radiation generation point (plasma 5) can be achieved. The large distance results in a long life for these components. Particularly for the target nozzle 133 as well, the damage (corrosion) due to thermal radiation and particle radiation from the plasma 5 is greatly reduced, so that a stable supply of the target over a longer operating time at the interaction position 41 can be achieved. it can.

Because metal “fuel” (solid target) has the property of causing haze, its amount must be limited to that required to produce radiation. When using tin (Sn) having a strong spectral line at 13.5 nm, about 5 · 10 ¹⁴ for an EUV source size of 0.5 mm in diameter with an excitation energy of about 1 J per excitation. Sn ions (corresponding to an ion volume of about 30 μm in diameter) are required. The source size is derived from the etendue (product of light emission area and spread solid angle) required in EUV lithography. The size adaptation of the small Sn volume before excitation to the required emission source size is significant when realized by the expansion of the prepulse beam 4 of energy. The energy required for this is 10 mJ, which is performed about 100 ns before the irradiation of the high energy pulse.

  When the frequency period is about 10 kHz, the in-band EUV (13.5 nm ± 2%) output of the source having the above parameters behind the focusing optical system reaches about 100 W. In this case, the daily consumption amount of Sn is about 85 g when the Sn amount is limited to the amount indispensable for the generation of radiation.

The ion density (and electron density) is determined for a homogeneous volume from only the optimal emission of EUV. This electron density is too low to efficiently absorb laser light having a wavelength of 1 μm. Therefore, the carrier gas 15 further functions as an electron donor in order to achieve a laser absorption rate of almost 100%. For nitrogen (N ₂ ) and argon (Ar), if it is a stoichiometric carrier gas, it is guaranteed about 2/3 or more. The stoichiometric ratio means the ratio of the number of atoms or the number of molecules of the target material and the carrier gas that occupies the volume of the element to be observed (bonded in the particles).

  In addition, by adding light noble gases (He, Ne), the emission spectral bandwidth of tin radiation is reduced to 13.5 nm. In the case of the pure tin which is not so, it greatly exceeds the required ± 2% (J. Opt. Soc. Am. B17 (2000) 1616, Choi et al.). Besides that, the proportion of radiation outside the desired EUV spectrum will also be significantly reduced.

  The true amount limitation of “fuel” (solid particles 14) to the amount essential for the generation of radiation is achieved because the frequency period to prepare the target volume depends on the energy pulse irradiation frequency (on the order of 10 kHz). It is limited only when there is an exact match, that is, only when exactly one target volume is supplied to the interaction position 41 for each generation of radiation. The deformation | transformation which produces | generates the droplet row | line | column 2 containing the particle | grains of the high frequency (typically 100kHz) shown in FIG. 1, stabilizing the frequency cycle of natural dripping by the pressure modulator 132 By way of example, in the following three embodiments, a single volume is removed (by various measures) from the produced too dense droplet row 2 resulting in a volume at the interaction location 41 (plasma 5). The frequency period is made to coincide with the energy pulse frequency.

FIG. 2 shows an example of such a configuration of an EUV source, where the energy beam 4 should be assumed to be laser light 42-without limiting generality.
The target supply apparatus 1 “thinches” the dense rows of droplets 23 to accurately adapt the frequency cycle of the droplets 23 at the interaction position 41 with the laser light 42 to the frequency cycle of the laser pulse train. For this purpose, the injection unit 13 is supplemented with respect to FIG. 1 by connecting an electrical deflection device 136 and a suction device 137 downstream of the outlet of the nozzle front chamber 135. The surplus droplet 23 is sucked by the suction device 137 and supplied to the liquefaction chamber 12 again. Thereby, unlike the embodiment of FIG. 1, the surplus droplets 23 may be partially vaporized in the vicinity of the plasma 5 or may generally contribute to an increased gas load in the plasma generation chamber 3. It is avoiding.

In the second modification (shown in FIG. 3), the droplets 23 containing particles are already generated in exact agreement with the pulse frequency of the laser light 42. FIG. 3 shows a modified droplet selection scheme for this purpose, in which the nozzle front chamber 135 is provided with a pressure ρ _antechamber approximately equal to the gas pressure ρ _{carrier gas} supplied to the mixing chamber 11. A pressure compensation unit 138 is connected. As a result, the droplet 23 is triggered by the pressure modulator 132 at exactly the same period as the pulse frequency of the laser beam 52, and as a result, each pulse laser beam 42 is transmitted from the ejection device 13 to all liquids. As many droplets 23 as the number corresponding to the droplets 23 are ejected.

This is because the nozzle front chamber 135 placed after the target nozzle 133 of the injection unit 13 is connected to the pressure compensation unit 138 adapted to the gas supply pressure pressure ρ _{carrier gas} to the mixing chamber 11, thereby achieving high reliability. As a result, the liquid droplet 23 does not accidentally drop from the liquid target material into the plasma generation chamber 3 without a short time pressure increase in the nozzle chamber 134 by the pressure modulator 132. I am doing so. This pressure modulator 132, which may be a piezo actuator, for example, attached to the nozzle chamber 134, generates a pulse pressure having the same period as the energy pulse frequency, i.e. if necessary (triggered pulsed laser light 42). Only the individual target 23 is prepared.

FIG. 4 shows a droplet selection method that has the same effect as that shown in FIG. 3 and that the individual targets 23 are assigned exactly one by one to each pulsed laser beam 42. However, in this embodiment, in order to allow only the n-th droplet 23 to pass through the plasma generation chamber 3, mechanical means taking the shape of a rotary perforated shielding plate 32 is provided. The rotary perforated shielding plate 32 is simultaneously a member of a case wall surface that separates one front chamber 31 from the plasma generation chamber 3, in which the front chamber 31 (the nozzle front chamber 135 of each of the above-described embodiments). High pressure ρ _oantechamber is set. Therefore, in this embodiment, the separate nozzle front chamber 135 of the injection unit 13 can be eliminated.

  In FIG. 4, the droplets 23 captured by the rotary perforated shielding plate 32 every other place, sublimated or vaporized there, and sucked out from the front chamber 31 by a separate pump unit (not shown). Shown stylized. Under actual circumstances, there are approximately every nine droplets 23 that pass through this and reach the position of interaction with the laser beam 42.

  As already mentioned above, it is significant that the solid particles 14 are added to the carrier gas 15 already liquefied in advance. FIG. 5 shows such a structure. In this embodiment, unlike the previous embodiments, the mixing chamber 11 and the liquefaction chamber 12 are arranged with their positions interchanged. In addition, the carrier gas is supplied into the liquefaction chamber 12, and the liquefied gas 17 prepared there is introduced into the mixing chamber 11 and mixed with the solid particles 14. Yes. Other configurations are the same as those shown in FIG. 1, but can be realized in accordance with the embodiment shown in FIGS.

  FIG. 6 shows a preferred modification of the present invention. In this case, it is assumed that the solid particles 14 having high luminous efficiency are already mixed with the carrier gas 15 in the mixing chamber 11 functioning as a reservoir. In order to disperse the particles 14 from the prepared particles (not shown), and to charge the particles 14 into the gas stream, the particles 14 are separated one by one from the particles in the state of rotation by a rotating brush. It is stripped off and delivered to the flow of carrier gas 15 which strokes it. In the process of the subsequent flow of the gas flow, the separation of the particles is avoided by appropriately configuring the conduit through which the carrier gas is guided.

  In that case, the pipe line extending from the mixing chamber 11 toward the injection unit 13 is further connected to another carrier gas pipe at the connection point (+) and the respective gas flows upstream of the connection point (+). Are connected to each other by the flow regulator 18 so as to be feedback-controlled.

  In order to calculate the control amount, a measuring device 19 placed behind the connection point (+) is used. The measuring device 19 measures the actual mixing ratio through measurement of scattered light, for example, and clean carrier gas 15 and A control variable for relatively adjusting the supply amount of the mixture 16 containing particles is sent out. This additional addition of the carrier gas adjusts the amount of solid particles 14 per unit volume of the carrier gas 15 very accurately, so that the effective target amount (particles 14) per droplet 23 of liquefied gas produced therefrom. Highly accurate dispensing is possible.

FIG. 6 shows that the supply pipe of clean carrier gas 15 and particle-containing mixture 16 routed to the connection point (+) both have a flow regulator 18. It may be sufficient to provide one flow regulator 18 in any one of these, preferably in the carrier gas supply pipe. In addition, in FIG. 6, the measuring device 19 that directly affects the pressure adjustment on the upstream side of the liquefaction chamber 12 is also _used for pressure adaptation control of the pressure ρ _antechamber in the nozzle front chamber 135. Can be used. Therefore, in that case, according to the embodiment of FIG. 4, a drop 23 is prepared only when necessary (drop-on-demand method), ie in accordance with the pulse frequency period of the laser light 42. Pressure adaptation control is possible.

1 is a schematic diagram of an EUV light source based on an energy beam in which a mixture of metal particles in a carrier gas is liquefied and supplied to an ejector, and a droplet train is generated by a droplet generator synchronized with a pulsed beam of energy. In order to “decimate” the droplet flow and precisely match the frequency of the droplets in the plasma generation region to the frequency cycle of the laser pulse train, the jet nozzle is followed by an electrical deflection device and a pump device. 2 shows a configuration example of the EUV light source shown in FIG. 1 based on laser-produced plasma (LPP). The nozzle chamber behind the injection nozzle has a carrier gas supply pressure almost equal to that of the plasma generation chamber, in order to generate droplets accurately and synchronously with the laser frequency pulse by the pressure modulator in the nozzle chamber. Fig. 2 shows a preferred implementation of an EUV light source according to the present invention connected to a pressure compensator providing equal pressure. In order to adapt the drop frequency at the interaction position to the laser frequency pulse, a mechanical device (chopper) for “thinning” the drop train is placed behind the target nozzle, in addition to the LPP light source. The form of is shown. Yet another modification of the EUV light source according to the present invention, in which a clean carrier gas liquefied in a mixing chamber is already mixed with solid particles and is supplied to a jetting device to produce a predetermined row of droplets. An example is shown. A pipe connection point with another carrier gas supply pipe is provided on the downstream side of the mixing chamber. In order to perform feedback control of the particle density and the gas pressure, the connection point is set by a measuring device placed behind the connection point. FIG. 6 shows yet another example of the configuration of an EUV light source according to the invention in which the flow regulator of the supply pipe routed in FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Target supply apparatus 11 Mixing chamber 12 Liquefaction chamber 13 Injection unit 131 Droplet generator 132 Pressure modulator 133 Target nozzle 134 Nozzle chamber 135 Nozzle front chamber 136 Deflection device 137 Suction device 138 Pressure compensation part 14 (solid) particle 15 Carrier gas 16 Mixture containing particles 17 Liquefied gas 18 Flow rate regulator 19 Measuring device 2 Droplet row 21 Target shaft 22 Target jet (jet)
23 Individual targets (droplets)
3 Plasma generation chamber 31 (Plasma generation chamber) front chamber 32 (rotary) perforated shielding plate 4 energy beam 41 interaction position 42 laser beam 5 plasma ρ pressure

Claims (21)

A structure for generating extreme ultraviolet rays from a plasma with high conversion efficiency generated by an energy beam, an energy pulse beam is directed to an interaction position with a target in the plasma generation chamber, and the target supply device emits light A mixing chamber for forming a mixture of particles of efficient target material and at least one carrier gas, and a target material with high luminous efficiency supplied to the interaction position in an amount that can be converted into radiation by an energy pulse. In order to be able to do so, in a structure having an injection unit for metering and discharging a predetermined target volume into the plasma generation chamber,
The target supply device (1) has one gas liquefaction chamber (12), wherein the target material is a mixture (16) of solid metal particles (14) in a liquefied carrier gas (15), Being supplied to the injection unit (13); and
A droplet generator (131) comprising a nozzle chamber (134) and a target nozzle (133) for generating a predetermined droplet size and droplet row (2); In order to produce a time-controlled row (2) of droplets (23), the ejection unit (13) has a frequency-dependent trigger triggered by the pulse frequency of the energy beam (4). A structure, characterized in that controllable means (132, 135, 136, 137, 138; 31, 32) are connected.   The liquefaction chamber (12) according to claim 1, wherein the liquefaction chamber (12) is arranged such that the solid particles (14) are sent to the liquefaction chamber (12) and mixed with the carrier gas (15). 11) A structure, characterized in that it is arranged downstream of 11) and the liquefaction chamber (12) is configured to liquefy said mixture (16).   2. The structure according to claim 1, wherein the liquefaction chamber (12) is arranged upstream of the mixing chamber (11) so that the liquefaction chamber (12) liquefies a clean carrier gas (15). And the mixing chamber (11) is configured to mix the solid particles (14) with a liquefied carrier gas (17).   2. The structure according to claim 1, wherein the solid particles (14) with good luminous efficiency are made of tin or a tin compound.   2. Structure according to claim 1, characterized in that the solid particles (14) consist of lithium or a lithium compound.   2. The structure according to claim 1, wherein the size of the solid particles (14) with good luminous efficiency is less than 10 [mu] m.   2. Structure according to claim 1, characterized in that the carrier gas (15) is a noble gas, preferably argon.   2. A structure according to claim 1, characterized in that the carrier gas (15) is nitrogen.   In the structure according to claim 1, a light noble gas is additionally added to the carrier gas (15) selected as the main component in order to restrict the emission spectrum bandwidth of EUV to around 13.5 nm. A structure characterized by that.   2. Structure according to claim 1, characterized in that the diameter of the individual droplets ejected from the ejection unit (13) is between 0.01 mm and 0.5 mm.   2. The structure according to claim 1, wherein said injection target is used to precisely match the frequency period at which each individual target (23) reaches the interaction position (41) with the pulse frequency of the energy beam (4). Structure, characterized in that means for removing said individual target (23) are arranged downstream of the target nozzle (133) of the unit (13).   12. The structure according to claim 11, wherein an unnecessary individual target (23) from the droplet row (2) discharged from the target nozzle (133) is provided downstream of the target nozzle (133) of the injection unit (13). The structure is characterized in that electrical deflection means (136) are arranged to deflect sideways by selection.   12. The structure according to claim 11, wherein the individual target (23) from a droplet row (2) discharged from the target nozzle (133) downstream of the target nozzle (133) of the jet unit (13). A structure, characterized in that mechanical closing means (32) are arranged to shield or pass through in a predetermined manner.   2. The structure according to claim 1, wherein the droplet generator (131) of the ejection unit (13) can temporarily increase the chamber pressure to eject individual droplets (23) as required. Therefore, a pressure modulator (132) disposed adjacent to the nozzle chamber (134) is provided, and a nozzle front chamber (135) is disposed downstream of the target nozzle (133). At this time, unless a pulse pressure is generated by the pressure modulator (132), in order to prevent undesired dripping of the target material from the target nozzle (133), it is higher than the plasma generation chamber (3), and the A structure characterized in that it is adjusted in the nozzle front chamber (135) to a pressure adapted to the gas pressure of the gas supply in the mixing chamber (11).   15. The structure according to claim 14, wherein the gas supply pressure in the mixing chamber (11) is adjusted slightly higher than in the nozzle front chamber (135) in order to adapt the pressure in the nozzle front chamber (135). A structure characterized by that.   2. The structure according to claim 1, wherein the particles (14) are prepared in sufficient quantity in one reservoir and are switchable in series for continuous injection into the plasma production chamber (3). Structure, characterized in that it is sent to a plurality of parallelly arranged mixing chambers (11) connected to the injection unit (13).   The structure according to claim 1, wherein the particles (14) are present in a mixed state with the carrier gas (15) in one mixing chamber (11), and are downstream of the mixing chamber (11). In addition, a pipe connection point with another carrier gas supply pipe is arranged, and at this time, at least one of the supply pipes routed to the connection point has a flow rate regulator (18). In order to adjust the mixed carrier gas (16) and the clean carrier gas (15) to a desired mixing ratio, the flow regulator (18) is disposed downstream of the connection point. A structure, characterized in that it can be controlled by a measuring device (19) for calculating the amount of particles in the gas stream.   18. Structure according to claim 17, characterized in that the measuring device (19) for controlling the mixing ratio is an optical unit for measuring scattered light.   2. A structure according to claim 1, characterized in that the pulse beam (4) of energy is at least one laser beam (42).   2. Structure according to claim 1, characterized in that the pulsed beam of energy (4) is an electron beam.   2. Structure according to claim 1, characterized in that the pulsed beam (4) of energy is an ion beam.

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